This invention relates to calcination of particulate carbonaceous material such as delayed petroleum coke. Delayed petroleum coke is generally calcined at high temperature to drive off volatile hydrocarbons and moisture. The calcined product may be used to produce anodes for aluminum manufacture, and in cases where the delayed coke is premium type coke, it is used for manufacture of graphite electrodes useful in the electric arc steel-making process.
Most present-day commercial coke calciners are inclined rotary kilns. The operation of this type of rotary calciner is described in U.S. Pat. Nos. 4,022,569 and 4,053,365.
Vertical shaft kilns have been used for calcining coke. British Pat. No. 770,930 and U.S. Pat. No. 3,433,713 describe externally-fired gravity-flow shaft kilns for calcining coke. These kilns include burners which heat the exterior of the calciner.
An internally-fired vertical calcining kiln is described in U.S. Pat. No. 3,823,073. This patent described a process in which the coke is calcined in a free-fall zone for a very short time period.
A vertical kiln which is heated by electrical resistance heating is described in U.S. Pat. No. 1,671,673.
A calcining process in which coke and oxidant are moved cocurrently through a vertical retort is described in U.S. Pat. No. 3,271,268.
Numerous U.S. patents describe vertical retorts for distilling oil from shale, and include use of recycle gas for cooling retorted product, air injection to provide an internal combustion zone, and use of combustion gas to preheat the feed. Exemplary of these U.S. Pat. Nos. are 2,560,767; 2,901,402; 3,297,562; 3,499,834 and 3,526,586. Additional U.S. Pat. Nos. showing shale retorting in internally-fired vertical furnaces include 2,813,823; 3,464,913; 3,619,405 and 4,066,529.
Processes for desulfurization of petroleum coke by passing the coke through heating, soaking and cooling zones are described in U.S. Pat. Nos. 2,716,628 and 2,789,085.
A process for making metallurgical coke for use in blast furnaces from a coking coal using a shaft kiln is described in U.S. Pat. No. 4,002,534.
None of the above references shows a process or apparatus for calcining delayed petroleum coke in an internally-fired vertical shaft kiln utilizing a downwardly moving bed of particulate coke and a countercurrent gas flow.